a fictitious name used in legal proceedings for a male party whose true name is not known, used especially as the second such name when two male persons are involved whose real names have not been ascertained.

"John Doe" (for males) and "Jane Doe" (for females) are multiple-use names that
are used ... This usage is mocked in the 1834 English song "John Doe and
Richard Roe": Two giants live in Britain's land, John Doe and Richard Roe,